1. Field of the Invention
The present invention relates to a thin film transistor, a method for manufacturing the thin film transistor, and a display device to which the thin film transistor is applied.
2. Description of the Related Art
As a kind of field effect transistor, a thin film transistor in which a channel region is formed in a semiconductor layer formed over a substrate having an insulating surface is known. Techniques in which amorphous silicon, microcrystalline silicon, or polycrystalline silicon is used for the semiconductor layer used in the thin film transistor have been disclosed (Patent Documents 1 to 5). A typical application of thin film transistors is a liquid crystal display television device, in which thin film transistors are put to practical use as switching transistors for each pixel that constitutes a display screen.